As an error correction technique in the real time IP image transmission, conventionally, Forward Error Correction (FEC) was implemented. In the FEC, because normal data packets and an FEC packet for the error correction are transmitted from an encoder to a decoder, even when one packet is missed, it is possible for the decoder to recover the one missed packet. However, when two or more packets are missed among the data packets, which are covered by one FEC packet, a retransmission request is transmitted to the encoder by Automatic Repeat reQuest (ARQ) to obtain missed packets from the encoder. Thus, the retransmission request is always transmitted by ARQ for the missing of two or more packets. Therefore, following problems occur. Namely, redundant packets are transmitted between the encoder and decoder, the load of the network increases, and the data recovery is failed when the buffering time in the decoder is short and the number of retransmission times is a few.
By the way, there is a technique enabling to enhance the service quality without negatively affecting respective services each other when plural services including a video streaming delivery service and a di-directional image communication service coexist. Specifically, a video streaming quality measuring unit of a user terminal obtains quality parameters for the video streaming, a di-directional image communication quality measuring unit obtains quality parameters for the di-directional image communication, and an FEC quality measuring unit obtains quality parameters for the error correction by FEC encoder/decoder and quality parameters for the communication for which RTP encapsulation is made. A receiving rate judging unit of a quality management server receives the quality parameters, and judges the receiving rate of the user terminal. Then, an encode rate controller controls the encode rate held by the user terminal according to the instruction from the receiving rate judging unit. However, there is no consideration for the interleave transmission of packets.
Moreover, there is a technique enabling to reproduce video and/or voice in the optimal delay time while suppressing unnecessary transmission of the retransmission requests, by controlling, in a packet receiving apparatus such as a decoder apparatus, which supports both of FEC and ARQ, transmission timing of the retransmission request, when the packet loss occurs. Specifically, the decoder apparatus has an error correction unit that carries out an error correction processing to recover the missed packet based on a redundant packet received next by a packet receiving unit when the missing of the packet is detected; a retransmission request sending unit that can send the retransmission request of the missed packet to the packet sending apparatus; and a retransmission controller that controls the transmission timing of the retransmission request to the packet sending apparatus by the retransmission request sending unit according to whether or not the missed packet can be recovered by the error correction unit within a predetermined time. However, there is no consideration for the interleave transmission of the packets.
Furthermore, there is a technique, which supports scalable and reliable multicast in a wireless network having large bandwidth delay product. In this technique, the same time slot is allocated to confirmation response packets from various receivers, which receive the loss of the same number of data packets. This method can be combined with other loss recovery techniques such as the recovery by the Forward Error Correction (FEC), preliminary protection, feedback suppression and collision detection. Because a method for using the bandwidth relates to only the number of transmitted packets, not the number of receivers, the scalability is realized. However, there is no consideration for the interleave transmission of the packets.
Moreover, there are a technique suppressing influence of the loss of packets to a reproduction function in a system that transmits real time consecutive stream to a packet communication network in which the loss of the packet is inevitable because the fluctuation of the transmission delay is large and a technique enabling to carry out buffering amount control to cope with a case where packets, which reached over the maximum permissible delay time, are consecutively discarded. Specifically, an apparatus has media input means that can communicate through a network or the like with a receiving terminal that receives and reproduces data and inputs and stores media data; media data compression means that compresses data inputted and stored by the media input means; packet transmission means that generates and transmits packets from the media data compressed by the media data compression means; receiving means that receives packet discard information; transmission mode determining means that determines, according to the packet discard information, whether or not cross-interleave of the transmission data should be carried out; and cross-interleave means that carries out the cross-interleave processing for the transmission data. When the packet discard information, which represents one of arrival states of the packets of the transmission data, which are transmitted from the packet transmission means and for which the cross-interleave processing is not carried out, is received from the receiving terminal and it is determined that the cross-interleave should be carried out, the data packets for which the cross-interleave processing is carried out. However, there is no consideration for the specific adjustment for the packet interleave and the adjustment of the interleave pattern based on data of the receiving side, such as the buffering time.
Such conventional techniques cannot transmit data to be transmitted in real time, according to states of the loss of packets (or missing of packets) while suppressing the calculation amount and the increase of the consumption of the network bandwidth.